It is known to coat an article such as a mug, teapot or dish with thermochromatic ink such that, when the article undergoes a temperature change by, for example, hot liquid being poured therein, an image disposed on the article becomes visible as the thermochromatic ink becomes transparent, and when the article cools, the image “disappears”. Also known are thermochromatic inks that change from opaque to transparent as the temperature changes from hot to cold. With such inks, images can be made to “disappear” when the article is heated.
In some cases, the coated article is covered with a pre-applied decoration that is covered by the thermochromatic ink coating. In other cases, the coating can be applied to an undecorated article and then a decoration can be sublimated into the coating.
U.S. Pat. No. 5,223,958 to Berry describes a well-known article that incorporates thermochromatic ink in an amusement device that is heat activated. Berry's amusement device comprises a supporting substrate, a layer of micro encapsulated thermochromatic liquid crystal material disposed on the substrate and an outer transparent film having a message or visual image. The requirement of a separate layer to carry the image, however, contributes to increased manufacturing costs in terms of both materials and process steps. Moreover, the Berry reference fails to provide any sort of protection for the transparent film. That is, the transparent film easily can be damaged by scratching or the like. Moreover still, an article manufactured in accordance with the disclosure of Berry is deficient in that no protection is afforded when the article is subjected to relatively harsh conditions, such as those presented by an automatic dishwasher.
U.S. Pat. No. 5,219,625 to Matsunami et al. is similar to Berry and discloses a thermochromatic laminate member having a base layer, a thermochromatic layer, and a thin transparent iridescent film laminated on the thermochromatic layer. Color patterns on the film become visible once the thermochromatic layer becomes clear after heating. An article fabricated in accordance with Matsunami et al., however, like an article made in accordance with Berry, requires a separate transparent film over the thermochromatic ink and, further, is susceptible to harsh conditions, wherein the laminate and even the thermochromatic ink layer can be damaged.
U.S. Pat. Nos. 6,759,099 and 6,902,775 to Lodge disclose decoration methods using thermochromic ink wherein a first coating having thermochromic ink is applied to an article to be decorated, the first coating is set or cured, and a second transparent coating material is applied over the first coating to protect it. This decoration method requiring multiple steps and two coatings is time consuming, complicated and thus expensive.
U.S. Pat. No. 6,281,165 to Cranford discloses a thermochromatic ink covered article and method making the same wherein a thermochromatic ink layer is disposed on the article, a protective coating is applied over the thermochromatic ink layer, and a design is disposed at least partially in the protective coating. This method is subject to the same disadvantages as the method disclosed in the Lodge patents in that it requires multiple manufacturing steps and two coatings to be applied to the article.
The thermochromatic pigment covered article and method of coating the same in accordance with the present invention are not subject to the disadvantages of the articles and methods disclosed in the above-identified patents, and embody improvements and advantages that are not disclosed or suggested by the above-identified patents or other prior art. More specifically, the present invention provides a thermochromatic pigment covered article and method wherein only a single coating is used that includes an encapsulated thermochromatic pigment contained within a resin in a manner that helps to protect the pigment and prevent the separation of the pigment and the resin.